Abstract

We report our discovery of the dynamic change in light-regulated hardness in an SrTiO<inf>3</inf> single crystal. Vickers hardness and atomic force microscope measurements reveal that the hardness is surprisingly increased and decreased with on and off irradiation for a (110), but unchanged for a (100) oriented single crystal. The dynamic change of light-regulated hardness is primarily governed by a higher concentration of photo-induced oxygen vacancies in the (110) crystal compared to the (100), as revealed by photoelectron spectroscopy. This work provides an undiscovered route toward controlling the dynamic change of hardness, which may offer alternative strategies to tune the localized deformations in polycrystalline metal oxides.